Ignitron temperature responsive arrangement



May 9, 1961 J. zEHNER IGNITRoN TEMPERATURE RESPONSIVE ARRANGEMENT Filed Feb. 2, 1959 llll r 1h. L lr.

nited States Patent C)fi IGNITRON TEMPERATURE RESPONSIVE ARRANGEMENT James L. Zehner, Schenectady,-N.Y., aignor to General Electric Company, a corporation of New York Filed Feb. 2, 1959, Ser. N0. 790,686

7 Claims. (Cl. 313-13) My invention relates generally to enveloped devices subject to heating during operation and requiring cooling for satisfactory operation and, more particularly, to devices such as electric discharge devices which are ordinarily cooled by the passage of a coolant through a coolant chamber associated therewith.

Many enveloped devices which are subject to heating, such as electric discharge devices of the ignitron type, are cooled by constructing the enveloping member or envelope with spaced inner and outer wall sections to provide a chamber for having a coolant, such as water, circulated therethrough. In such an arrangement it is desirable to provide means for assuring maximum cooling in the regions which are most effective in controlling the vapor pressure in the device. It is also desirable to provide means for controlling circulation of the coolant in rapid response to temperature changes of the device, thereby to conserve coolant and insure operation of the device within a predetermined desirable safe operating temperature range.

A primary object of my invention is to provide an improved envelope structure adapted for being cooled by a circulating coolant and effective for better controlling the cooling of predetermined regions of the envelope.

Another object of my invention is to provide a new and improved arrangement for controlling the circulation of a coolant through a coolant chamber of an enveloped device and effective for controlling the circulation of coolant in accordance with temperature changes in the device.

Another object of my invention is to provide, with an enveloped device subject to heating and having a chamber through which a coolant is circulated for cooling the device, a new and improved fast-acting temperature responsive arrangement for controlling the coolant circulation so as to insure operation of the device within a predetermined safe operating range.

Another object of my invention is to provide an improved electrical discharge device having an envelope containing vapor and including inner and outer walls defining a coolant chamber and means for sensing a discrete area ofthe inner wall which is closely representative of the vapor-controlling temperature in the device.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specication.

In carrying out the objects of my invention I provide an envelope housing a device including a mercury vapor atmosphere and subject to heating. The envelope includes inner and outer walls defining a chamber for Patented May 9, 1961 coolant path through the chamber. The pitch of the path varies along the length of the envelope and is smallest in the region of a pool-type cathode located in one end of the envelope. At a point on the corrugation an area of the outer wall straddles the corrugation and is substantially depressed and apertured with the rim of the aperture extending inwardly and bonded to the inner wall to define a discrete area of the inner wall closely representative of the vapor-controlling temperature in the envelope. A high-thermal conductivity member is inserted in the apertureand bonded to the mentioned discrete area of the inner wall. The lateral surface of the high-thermal conductivity member is spaced from the inwardly extending rim portions of the outer wall and a thermally responsive control means is provided for contacting the outer end of the high-thermal conductivity member. As desired, the thermally responsive control means can control either the coolant circulating through the chamber or the operation of the device contained in the envelope.

For a better understanding of my invention reference may be had to the accompanying drawing in which:

Figure 1 is a side elevational view of an electric discharge device of the ignitron type incorporating my invention and partially broken away to illustrate certain features of the device; and

Figure 2 is an enlarged fragmentary sectional view illustrating certain features of my invention in greater detail.

Referring to the draw-ing, I have shown in Figure 1 my invention as applied to an electric discharge device of the ignitron type including an elongated cylindrical envelope 1. e The envelope 1 is preferably formed of stainless steel, which is a low-thermal conductivity metal as compared with some other metals such, for example, as copper, and includes `spaced inner and outer walls 2 and 3, respectively, for defining a coolant chamber generally designated 4.

The envelope is closed at its upper end by a header assembly generally designated 5 including an anode seal 6 for supporting a generally cylindrical positive electrode or anode 7 centrally within the upper end of the envelope. As is well understood, the seal construction supports the anode in insulative relation with respect to the envelope. Also provided is an externally accessible anode terminal 8. The anode, in accordance with common practice in electric discharge devices of the presently-disclosed type, can be formed of graphite.

The opposite end of the envelope is closed by a cupshaped header 10 which is welded to the lower end of the inner wall 2 to form a hermetic seal. The negative electrode or cathode of the device is conta-ined in the envelope and is provided by a pool of conducting liquid, indicated by the numeral 11, which to advantage may be mercury, An ignitor or starting electrode 12 is suitably mounted in the lower end of the device for cooperating with the mercury to provide an initiating arc. A suitably mounted graphite baffle element 13 can be included for avoiding undesirable mercury splashing on the anode 7. In the operation of power conversion tubes of devices of this character, some of the cathode v1.1 is vaporized and an arc discharge is established between the surface of the cathode and the anode.

As will be readily appreciated by those skilled in the art, satisfactory operation of the device is obtained by cooling the envelope during operation of the device to condense the mercury vapor therein on the inner wall of the envelope and to cause it to flow back to the pool 11 thereof.

As seen in Figures 1 and 2, the inner wall 2 is straight and the outer wall 3 of the envelope `which is relatively thinner than the inner wall is formed with a helical corrugation 14. 'I'he corrugation 14 cooperates with the straight inner wall to provide a helical coolant passage between a coolant inlet *15 at the lo'wer end of the envelope and an outlet 16 at the upper end of the envelope. The 'pitch of the helical corrugation 1-4 diminishes from the upper end of the envelope toward the lower end with the efIect of providing the helical coolant passage with a varying cross-sectional area alo'ng the length of the envelope. Thus, the cross-sectional area of the coolant passage is smallest at the lower end of the Vdevice or in the region of the mercury pool 11 and increases toward the upper end or toward the outlet of the coolant passage. This arrangement has the desirable effect of providing greater cooling capacity in the region of the envelope which is most effective in determining the vaverage vapor pressure in the device and, specifically, in the region immediately about and above the level of the mercury pool.

In order to conserve coolant and to insure operation of the device within a predetermined satisfactory and safe temperature range, I have provided an arrangement illustrated in detail in Figure 2 and adapted for controlling the coolant circulation through the helical coolant passage in rapid response to temperature changes in the envelope. This controlling means includes a substantial depression 21 formed in the outer wall 3 on a point of the corrugation near the lower end of the device or in the region of the device which controls the Vapor pressure during operation. As perhaps better seen in Figure 2, `the depressed area. is apertured at 22 and the rim of the aperture extends inwardly and is bonded, as by a silver solder braze 19, to the outer surface of the straight inner wall, thus to define a substantial `discrete area of the inner wall designated 20 which is closely representative of the vaporcontrolling temperature in the device. Brazed in the depression 21 and in intimate contact with the outer surface of the inner wall, as by the silver solder braze 19, also, Ais a high-thermal conductivity member or plug 23. 'Ille plug '23 can be satisfactorily formed of copper and the optimum balance between the heat Iilow from the inner wall area 20 and the heat flow to the adjacent surface of the outer wall 3 is achieved by controlling the amount of silver solder used in making the braze between these elements.

The plug 23 is formed with an enlarged head 24 and provided for contacting the outer surface of the head 24 is a thermostatic switch 25. The switch V25 can comprise -any thermostatic` device of the type generally available and adapted for contacting a heated surface and operating in close response to the temperature changes thereof to control a circuit therethrough in response to the temperature changes. 'Ihe switch 25 is provided with a pair of arms 26 and spring loaded attaching elements 27 adapted for cooperating, for example, with a pair of oppositely extending bifurcated lugs 28 mounted, as by welding, to the outer wall 3.

The switch 25 is connected in a circuit in a power source 30 controlled by a master switch 31, and included in the circuit is an electrically controlled iluid ilo-w valve 32, which, for example, can be a solenoid-operated llow valve.

In operation, the inner wall of the device becomes heated in an amount directly proportional to' the average heat dissipation in the. envelope with the result that the area 20 of the inner Wall defined by the aperture 22 in the outer wall 3 becomes heated to an amount closely representative of the vapor-controlling temperature in the device. This heat ilows .directly to the high-.conductivity member or plug 23 which isheld in intimate thermal co'ntact by the solder braze between the elements. Additionally, due to the fact that a controlled amount of solder braze provides optimum thermal contact to the adjacent surface of the outer wall 3, the resulting temperature of the plug 23 closely approximates the average vapor-controlling temperature in the envelope. In Aother words, the high-conductivity plug 23, although it is located on the temperature of the inner surface of the device at the point which is effective in controlling the average vapor pressure in the device. The amount of solder used about the plug 23 can be adjusted readily until the optimum thermal contact to the edge of the aperture in the outer wall is attained. As a result, the temperature of the cap 24 formed on the plug 23 is substantially closely representative o-f the temperature of the inner wall area 20 which, in turn, is closely representative of the temperature in the device in the region just above the cathode, with the result that the switch 25 is adapted fo'r operating substantially rapidly in response to temperature changes in the device in the region just above the cathode.

'I'.he disposition of the depression 211 for receiving the plug 23 in the corrugation 14 serves effectively to avoid the necessity of providing a depression which would create substantial impedance to the coolant flow through the spiral chamber. In other words, by disposing the depression 21 at a point where it straddles the corrugation, it does not block substantial flow of .the coolant through any single spiral portion of the path.

lIt will be seen that by providing my structure with the described means for insuring rapid coolant ow in the lower region of the envelope where the vapor pressure is determined during operation it is possible to obtain better operation of the device by having better control of the coolant '.llow in response to' temperature change in the critical region of the device. Additionally, by providing my structure with the `described means for sensing temperature at the inner wall of the envelope in the mercurycondensing region of the device and in a manner as to be responsive to temperature changes of the inner wall without uncertainties generally encountered in prior art devices where substantial resistance to heat flow can be introduced through loose or oxidized joints, my arrangement is adapted for being more closely responsive totemperature changes in the envelope. Thus, coolant can be conserved and operation of the device Within a well-delined predetermined and safe operating range can be readily obtained.

It twill lbe seen further that while I have shown the temperature responsive portion of my invention applied to the control of the coolant ow, it is equally applicable for controlling the operation of the device in response to temperature changes. For example, the switch 25 or another cooperating with a similar heat conductive element such as the element 23 in Figures l and 2, can be effectively employed for controlling the current flow through the tube, thus to provide a protective arrangement for the tube adapted for operating when a dangerous temperature condition is encountered.

It will be seen still further that while I have shown my invention applied to an electric discharge device of the ignitron type, it is equally applicable for controlling the cooling and over-temperature protection of any envelope device which is subject to heating.

While I have shown and described a specific embodiment of my invention, I do not desire my invention to be limited to the particular form shown and described and I intend by the appended claims to cover all modications within the spirit and scope of my invention.

What I claim as new and ydesire to secure by Letters Patent of the United States is:

l. An electric discharge device comprising an envelope, an electrode arrangement in said envelope adapted for generating substantial heat in one end of said envelope during normal operation, said envelope comprising a pair of inner and outer walls defining a chamber for having a coolant circulated therethrough, `and means deiining a helical coolant path between said walls and of varying cross-sectional areas in planes perpendicular to the direction of said path and along the tfull length of said path, said path having the smallest cross-sectional area in said one end of said envelope, thereby to laiford greater cooling the outside of the enveloped device, follows very closely capacity thereat to provide greater dissipation of heat from said electrode arrangement generating heat in said one end of said envelope and to minimize the coolant pressure drop across the chamber.

2. An envelope adapted for housing a device subject to heating, said envelope including inner and outer Walls defining a coolant chamber, said inner wall being straight, said outer wall including an inwardly extending depresslon and being lapertured in said depression with the rim of the aperture being sealed to the outer surface of said inner wall, thereby to define an area of said inner wall exposed through said aperture in said outer wall and representative of the temperature in said envelope, and thermally responsive means wholly external of said coolant chamber and operative in response to the temperature of the exposed area of said inner Wall.

3. An envelope adapted for housing a -device subject to heating, said envelope including inner and outer walls dening a coolant chamber, said inner wall being straight and including an inwardly extending depression, said outer Wall being apertured in said depression with the rim of the aperture being sealed to the outer surface of said inner wall, thereby to provide an 'area of said inner wall exposed through said aperture in said outer wall and representative of the temperature in said envelope, and a plug-like high thermal conductivity metal member disposed wholly external of said coolant chamber and secured to the exposed area of said inner Wall by a high thermal conductivity metallic bond, whereby said member is rendered representative of the temperature in said device and adapted -for having thermally responsive control means mounted thereon.

4. An electric discharge device comprising a plurality of electrode elements adapted for cooperating and generlating substantial heat during normal operation of said device, an envelope containing said elements and including inner `and outer walls deining a coolant chamber, said outer Wall including an inwardly extending depression and being apertured in said depression with the rim of the :aperture bonded to the outer sunface of said inner wall thereby to provide Ian Iarea of said inner wall exposed through said aperture in said outer wall and representative lof the temperature in said envelope, a member of high thermal conductivity material positioned in said aperture in said outer Wall and bonded to the exposed area of said inner Wall by -a metallic bond, said member being Wholly external of said coolant chamber and laterally spaced from the inwardly extending portions of said depression in said outer wall, a predetermined quantity of brazing material providing a predetermined -thermal path between the dateral portions of said plug and said outer wall, and a thermally-responsive control means intimately contacting said outer end of said member and operative in response to the temperature of said conductive member.

5. -An envelope adapted for housing a device subject to heating, said envelope including inner and outer walls defining a coolant chamber, said outer wall having a helical depression cooperating with said inner wall to define a helical coolant path in said chamber, said outer wall being apertured in said depression and having the rim of the aperture bonded to the outer surface of said inner Wall to dene a discrete area thereof exposed through the aperture in said outer wall and representative of the temperature of said envelope and adapted for being intimately contacted by thermally responsive control means Wholly external of said envelope and said coolant chamber.

6'. An envelope according to claim 5 wherein a high thermal conductivity member is bonded directly by a metallic bond to said discrete area oi said inner wall in laterally spaced relation to the inwardly extending portions of said depression in said outer wall for thereby being substantially representative of the temperature in said envelope, and a thermally responsive control means is held in intimate contact with said high thermal conductivity member for operating in response to the temper-ature thereof.

7. An ignitron comprising an elongated envelope, an anode located in the upper portion of said envelope, a pool-type cathode located in the bottom of said envelope, said cathode being adapted for having a portion thereof vaporized during operation of said ignitron, said envelope including inner and outer walls defining a coolant chamber, a helical corrugation in said outer Wal-l extending inward and engaging said inner Wall lfor defining Ia helical coolant path, said corru-gation having a v-arying pitch along the full length of said envelope to provide a coolant path of constantly varying cross sectional areas in planes perpendicular to t'ne direction of said path and along the full length of said path, thereby to Iaiord different cooling capacities at different regions of said envelope, said pitch being the smallest at the axial level of said envelope between said anode and cathode, thereby to afford greatest cooling capacity in that region, said outer wall being apert-ured in said region between said anode and cathode and in an area straddling said corrugation and having the rim of the aperture extending inwardly to deine a discrete area of said inner wall representative of a critical inner-wall temperature of said ignitron, Ia high thermal Yconductivity member positioned in said aperture and bonded directly to said Idiscrete area of said inner wall and having the outer portion thereof thermally connected to said outer wall through sufficient thermal resistance to insure that the temperature of the outer end of said member be representative of the critical inner-wall temperature of said ignitron under all conditions of coolant iiow through said chamber, and a thermally-re sponsive control means intimately contacting said outer end of said high-thermal conductivity member and operative in response to the temperature of said conductive member as determined by said critical inner wall temper-ature at said discrete area.

References Cited in the iile of this patent UNITED STATES PATENTS 1,900,013 Gebhard Mar. 7, 1933 1,985,511 Marti Dec. 25, 1934 2,042,183 Lubcke May 26, 1936 2,192,047 Miles Feb. 27, 1940 2,254,917 Schroder Sept. 2, 1941 2,438,004 Garbuny et al Mar. 16, 1948 2,461,275 Herskind Feb. 8, 1949 2,822,489 Zehner Feb. 4, 1958 

